Does an active DAS eliminate signal loss entirely?

No. Fiber loss over typical building-scale distances is small enough to be treated as negligible for design purposes, but it is not zero, and there are still RF-to-optical and optical-to-RF conversion losses at the head-end and each remote unit. The key difference from passive DAS is that each remote unit re-amplifies to its own full design output locally, so those losses don't compound across the whole system the way cascaded splitter and coax loss does.

Why not just use a more powerful donor or BDA to fix a passive DAS's range?

Boosting source power helps, but every stage between the source and the farthest antenna still divides that power the same way — a more powerful donor buys some extra margin, but doubling or tripling coverage area typically needs far more power than is practical or code-compliant, and eventually the cumulative splitter/coax loss for very long runs makes a passive design impractical regardless of source power.

Can a single building use both passive and active DAS?

Yes — this is common in hybrid designs. An active DAS head-end and remote units handle the building-wide backbone and long horizontal/vertical runs, while each remote unit feeds a small passive splitter network to cover its local zone. This combines active DAS's reach with passive DAS's lower cost and simplicity at the antenna level.

Does active DAS need electrical power at every remote unit?

Yes — each remote unit contains active amplification electronics and requires local power (often PoE or a dedicated circuit), plus standby battery backup where public-safety code requires continued operation during a power outage. This is a real cost and maintenance difference from a purely passive splitter/tap network, which has no powered components at the antenna nodes.

Which architecture is required for public-safety ERRCS coverage?

Neither architecture is mandated by code — NFPA 1221 and IFC 510 specify the coverage, signal strength, and survivability requirements a system must meet (such as −95 dBm minimum signal and battery/backup power), not the distribution technology. The choice between passive, active, or hybrid DAS is an engineering decision based on which approach can meet those requirements economically for the specific building.

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Concept Explainer · Radio Communications

Passive vs. Active DAS

Why the choice isn't "how many splitters" — it's whether the RF signal is distributed as-is over coax, or converted, carried on fiber, and rebuilt at every remote unit.

Every in-building distributed antenna system takes one RF source — a donor antenna, a BDA, a cellular carrier's base station — and spreads its coverage across a floor plate or an entire high-rise. How it does that spreading is the entire design decision. A passive DAS pushes the original RF signal down coax cable through purely passive splitters and taps, losing a little more power at every branch. An active DAS converts that signal to an optical or digital format, carries it over fiber with almost no loss, and regenerates full-strength RF locally at each remote unit. Same starting signal, two fundamentally different distribution architectures — and very different limits on how large a building they can cover.